Silicon carbide (SiC) power switches are known for their low switching losses. For various reasons normally-on SiC-JFETs seem to be suitable for low loss unipolar switch applications. However, for safety reasons a normally-off behavior is usually desired. Therefore, normally-on high voltage SiC-JFETs were combined with standard low-voltage MOSFETs thus forming a normally-off cascode circuit which is, for example, described in D. Domes, X. Zhang: “CASCODE LIGHT—normally-on JFET stand alone performance in a normally-off Cascode circuit,” in: Proceedings of PCIM 2010, Nuremberg, May 2010.
The mentioned cascode circuits may be used in power converters to high-voltage convert DC power into (e.g., multi-phase) AC power. Most applications use a 3-phase power converter (also referred to as 3-phase inverter) which is composed of three half-bridge circuits coupled in parallel. Such power converters may be usefully applied, for example, to drive synchronous or asynchronous electric motors, particularly in hybrid or electric vehicles.
Replacing each single normally-on SiC-JFET with a respective cascode circuit will, however, result in higher losses. Thus their remains a need for an improved power converter.